About Sims Purcell

Description

What Is Audi G28? History Of Audi G28
How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indication to the G5 Tachometer within the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jump in the chain link of the upper chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

It is a little tricky to test since there are various pins on the connector and they all have different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is at full operation. If you're having issues with this component, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the 4th one was dry. I put tissue over each injector hole, and when i turn the engine on without sparks, the three with gazoline jump right out. The fourth one remains shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. I'm assuming that the issue is somewhere else.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c even when i unplug it. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do. I think I've eliminated everything else. I'm afraid i may have missed something. If anyone has suggestions, please chime in! TIA!


3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. audi key programming -style transmitter is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. Test them out - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They should be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines must know both the position and speed of the crankshaft to determine timing of fuel injectors, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner that could cause engine shut down.

Some of the signs of a failing G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or misfiring when in gear. If you are experiencing any of these problems, it is most likely that your sensor is going bad and should be replaced. They're inexpensive and easy to locate, especially when they're a Bosch model like ours. Alternately, the GM version of this unit is also a good choice.

5. Tachometer

A failing engine speed sensor could be a cause for numerous issues in your vehicle. It's a crucial component of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the engine of the car is spinning. This sensor can cause the transmission to malfunction and other components in the car to be affected.

The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to regulate the flow of fuel and boost as well as timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a common component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.